A STUDY OF PERMANENT MAGNETS OF THE BARIUM FERRITE TYPE

摘要

Permanent magnets of the barium-ferrite type were investigated to improve the magnetic properties of the material and to add to the knowledge of the magnetization process. Magnets of the approximate composition BaO:6 Fe2O3 were prepared which had over 3.7 million gauss x oersted energy products. Various compositions of the ceramic together with some additions were experimentally tried. The numerous steps in the preparation of. oriented magnets were investigated to obtain better magnets. The development of successful methods enabled us to obtain better than 93％ crystal orientations and residual inductions of nearly 4200 gauss. A saturation magnetization of 4650 gauss was found possible for a density of 5.3 gm/cm3 (X-ray density). Fine particles were necessary to have high coercive forces.nOther magnetic phenomena related to barium ferrite were also studied. Magnets of oriented barium ferrite exhibited a greater, reversible variation in remanent induction with temperature than other common permanent magnet material. Joule magnetostriction was found to be not large and negative in sign. Pressure on barium ferrite magnets increased their remanent inductions by a few gauss.